Characterization of low energy Lu background on continuous LYSO blocks

The presence of the naturally occurring isotope ¹⁷⁶Lu gives rise to background count rates in LSO/LYSO crystals to be used in PET and SPECT systems. The aim of this work is to measure ¹⁷⁶Lu background count rates and its spatial distributions in a continuous LYSO block. Our results show that the low energy component of ¹⁷⁶Lu background is related to partial energy deposition mainly produced near the crystal edge showing a hot-perimeter artifact. Furthermore, ¹⁷⁶Lu background rate is observed to be ×10 times lower for a 100-180 keV than for a 411-611 keV energy window. Our findings indicate that when using monolithic LYSO crystal blocks, ¹⁷⁶Lu background is not expected to significantly deteriorate the performance of single photon detection systems.